What’s Next? Rhythm-Based Anticipation in Children with ASD

Background:

Information in the sensory environment tends to be highly predictive of upcoming events, allowing for online planning and decision-making. Numerous studies have shown that the neural processing of predictable stimuli is significantly facilitated compared to that of non-predictable stimuli. Clinical and anecdotal observations have led to the view that people with ASD have deficits in generating and/or applying predictions in their daily lives, and there is some empirical support for this notion. However, the underlying neural mechanisms are not yet well understood. In the face of rhythmic events, such as speech, music, or walking, brain oscillations become aligned with the rhythm - a process referred to as neural entrainment. This way, the brain interacts with environmental cues to prepare for upcoming events. Moreover, neural activity prior to a cued target, the Contingent Negative Variation (CNV), indicates how efficiently the brain is anticipating the upcoming event. A test of the integrity of these neural processes provides insight into what drives impairments of prediction in ASD.

Objectives:

Here we sought to assess the integrity of anticipatory process in a rhythmically cued environment, in children with ASD. To this end, we presented sensory stimuli in a cued context and measured cortical activity with scalp EEG, as well as psychophysics.

Methods:

Children with ASD (n=40) and age-matched controls (n=22), between 6 and 9 years old, were included. The groups did not differ significantly on age or IQ. Participants responded to an auditory stimulus that was either preceded by 4 isochronously presented visual stimuli (with all stimuli in one trial sequence presented at 1.5 Hz), or not. Due to their rhythmicity, the visual cues were highly predictive of the temporal onset of the auditory target stimulus. High density 64-channel scalp EEG (BioSemi) was recorded during the task, as was behavior. The EEG data was analyzed in both frequency and time domains, to examine the coherence of neural entrainment, and generation of the CNV.

Results:

We examined entrainment to the visual cues preceding the auditory target in the low-pass (1.9Hz) filtered data. While both groups showed entrainment at the stimulating rhythm (1.5Hz), this was significantly greater in the control compared to the ASD group. In the broadband data, the expected CNV was clearly observed in both groups, in the interval between the 4^th visual cue and the target. However, in the control group it onset 200ms earlier and was of greater amplitude compared to the ASD group. Thus while ASD can bring anticipatory processes online, this is severely delayed compared to controls. Of note, analyses revealed that the sensory evoked responses were highly similar across the two groups of participants.

Conclusions:

Anticipation of events is an adaptive function in the typical brain. Although children with ASD are known for atypical weighting of prior expectations relative to sensory inputs, the brain processes underlying this impairment are not well understood. The delayed anticipation and reduced entrainment to sensory cues that we see here offer evidence of the neural underpinnings of impaired event anticipation in children with ASD.